With two victories in the first three days of the Tour, Marcel Kittel already looks unstoppable. As Buckingham Palace loomed behind him, he had the strength and confidence to lead out the sprint finish of the Tour’s third stage from 250 metres out and sped up the middle of the Mall, constantly looking underneath and back, as if inviting Peter Sagan, Mark Renshaw and Bryan Coquard to try to emerge from his slipstream and attempt to come past him.

They stood no chance as the slightly downhill finish favoured whoever launched his effort first and Kittel was perfectly delivered by his Giant-Shimano team, the most cohesive in the final kilometres this year. Sagan – fastest of the also-rans – finished almost two bike lengths behind.

The Slovak wears the green jersey, awarded to the most consistent rider in the race, but he is not the fastest man in the race, and that by some margin.

A less confident sprinter than Kittel would have hugged one barrier so that he had to worry about the opposition passing on only one side, but the German was having none of that after his final lead-out man, John Degenkolb, peeled off. “It was more of a real sprinters’ stage today,” he said. “It wasn’t really hard, the finish was straight and wide in the last 500 metres and being slightly downhill it was perfect for me.”

Marcel Kittel waits to pounce on the sprint for the finish at the Mall in London. Photograph: Peter Dejong/AP

Whisper it to the ranks of British fans who would have hoped to see the sorely missed Mark Cavendish laying the ghost of the 2012 Olympics to rest here but there was a whiff of the confidence of the Manxman in his glory days of 2009 to 2012 about Kittel. In one Tour and three days, the German has taken his personal tally of stage wins to six and he will have three more opportunities before the race reaches the Vosges on Saturday, starting with Tuesday’s flat leg across northern France to Lille.

“The team delivered me to the perfect position in the finish,” said Kittel. “That meant I could choose to wait for the right moment.”

Just as Cavendish used to do, the German is ignoring the intermediate sprints that count for the points jersey so that he saves all his strength for the finish. His only worry in the short term, it seems, is the fact that Cavendish’s absence means that there is one fewer sprinters’ teams to make the pace through the stage; the Lotto team of his fellow German, André Greipel, have been most prominent in that role in the first two stages, and at some point they may decide to leave Kittel’s men to do the work.

The longer term brings other questions, however. It is likely that Giant will be left without a lead sponsor at the end of the season; in fact, they were left without a main backer last year after Argos Oil pulled out and their bike maker took over. They have recently been linked with a new squad being put together – reportedly at least – by the Spanish Formula One driver Fernando Alonso, but Kittel said he knows nothing of that. “There are a lot of stories about what Alonso’s plans are in cycling and I don’t know a lot,” he insisted.

“We have been talking to our team manager, Ivan Spekenbrink, and he has told us we will continue together, even without a sponsor. That’s all I need to know and I’m happy my future is assured.”

On the final day of the English Grand Départ, crowds were similar in volume to those in Yorkshire, against a contrasting backdrop, with Cambridge’s King’s Parade first up, then cornfields, village greens and half-timbered houses giving way eventually to ranks of suburban houses, the Olympic velodrome and the ArcelorMittal Orbit before the Docklands light railway and the Thames appeared, after which the stage became a high-speed tour of London’s most iconic monuments: Tower Bridge, the Embankment, Big Ben.

If there was no doubt about the winner, this was still a tense finish, but that was less down to the occasion than to the weather. When the Tour started in London in 2007, that weekend was the only dry one in that soaking summer, but here a shower late in the stage just before the riders arrived in central London came as if on cue to accentuate the glories of Yorkshire and made the final kilometres slippery and dangerous, underlined by a high-speed crash on the right-hander by Big Ben.

There were no threats to Vincenzo Nibali’s yellow jersey – the Italian continues in the maillot jaune on Tuesday – and the only significant escape of the stage featured the Czech Jan Barta and France’s Jean-Marc Bideau, who remained at the head of affairs from the outskirts of Cambridge, all the way through Essex, past the Olympic complex and Docklands light railway – complete with a train painted in yellow bearing the slogan Va Va Froome. Barta was the stronger of the duo in the latter part of the stage and he was scooped up only as the race passed the Tower of London with six kilometres remaining.

The run-in was a complex one due to the wealth of road furniture – as is the case on all the Tour stages that finish in major cities these days – and unfortunately the showers did not hold off, although the road was dry when the first crash happened 30km out, when a rider appeared to have hit a spectator, with the 2010 Tour de France winner Andy Schleck involved as well as the Australian Simon Gerrans, who has fallen at least once a day so far.

Other riders fell foul of a bus-lane divider while, at the front of the peloton in the final kilometres, favourites such as Alberto Contador could be seen sitting snugly behind their team-mates to stay out of trouble.